First-class install target + prompt-hook for ZCode (Z.ai)

[dogking95]

Request

Add ZCode (Z.ai's coding agent harness, https://zcode.z.ai) as a first-class --target for codegraph install, so codegraph install --target=zcode writes the MCP config automatically.

Related: tracking issue #649 (zcode is already listed there from #962). Opening a dedicated issue to attach the concrete config format and hook details so the target is easier to land.

Why

ZCode is a first-class MCP + hooks-capable agent. Today, ZCode users have to hand-edit the MCP config. CodeGraph works great once configured manually — the ask is just the one-command install target like the other agents have.

What ZCode needs

1. MCP server config (install target)

ZCode reads MCP servers from ~/.zcode/cli/config.json (user scope) or <workspace>/.zcode/config.json (workspace scope), under mcp.servers:

{
  "mcp": {
    "servers": {
      "codegraph": {
        "type": "stdio",
        "command": "codegraph",
        "args": ["serve", "--mcp"],
        "enabled": true,
        "timeoutMs": 60000
      }
    }
  }
}

That's it for MCP — same codegraph serve --mcp as everywhere else. A new file in src/installer/targets/ plus a registry entry, as you noted in #649.

2. (Bonus) UserPromptSubmit prompt-hook

ZCode also exposes a UserPromptSubmit hook that can inject context per turn. If CodeGraph shipped a prompt-hook for ZCode (analogous to what exists for Claude Code), it could inject relevant-symbols context on each prompt. This is optional — the MCP target alone is the main ask.

ZCode hooks docs: https://zcode.z.ai/cn/docs/hooks
ZCode plugin/MCP docs: https://zcode.z.ai/cn/docs/plugin

Config location summary

Scope	Path
User	~/.zcode/cli/config.json
Workspace	<workspace>/.zcode/config.json

Happy to test a PR on Windows if that helps.